Many dive venues have Manta Points and Bali is no exception.Many dive venues have Manta Points.
The one in Bali is really excellent.

Huge, friendly peaceful giants just gently floating overhead like space motherships, make for all the ingredients of an excellent dive site. point is at Nusa Penida, a small island on the south eastern side of Bali.

It is a bit of a long boat ride to the site from Bali, about one hour, but well worth it.

The huge mantas keep on passing over your head like giant space motherships.

The hour that you spend  in one spot watching them from  the bottom passes so quickly. It’s just wonderful watching these large gracious creatures glide past overhead in the water.

There are also many rays in the area.